Extraction and Purification, Structural Characterization and Biological Activity of a Polysaccharide, PRP-1, from Plumeria rubra

Polysaccharides derived from the flowers of Plumeria rubra (PRP) have shown a variety of beneficial effects on improving human health. However, the structural features and bioactivities of PRP remain unclear. A novel neutral polysaccharide (named PRP-1) with a molecular weight of 23 kDa was extracted and purified from the flowers of P. rubra. PRP-1 was consisted of arabinose, galactose, glucose, xylose and mannose, with a molar ratio of 1.49: 27.89: 50.24: 13.02: 7.36. The structural characterization based on the methylation and 1D/2D nuclear magnetic resonance analyses indicated that PRP-1 was composed of & RARR;4)-Glcp-(1 & RARR;, & RARR;4,6)-Glcp-(1 & RARR;, & RARR;4)-Galp-(1 & RARR;, & RARR;2)-Galp-(1 & RARR;, t-Gal(p), & RARR;4)-Manp-(1 & RARR;, & RARR;4,6)-Manp-(1 & RARR;, t-Man(p), & RARR;2)-Xylp-(1 & RARR;, and t-Xyl(p). Scanning electron microscopy revealed that PRP-1 possess a compact three-dimensional curling network structure in the terms of morphology. PRP-1 exhibited anti-inflammatory activity, which have moderate inhibitory effects on TNF-& alpha; and IL-6 production in lipopolysaccharide (LPS)-induced RAW 264.7 cells. In addition, PRP-1 showed ABTS, OH radicals scavenging and the Fe2+ chelating effects in a concentration dependent manner. In & alpha;-glucosidase inhibition assay, PRP-1 did not exhibit inhibitory activity. Overall, these results provide a scientific basis for the utilization of the flowers of P. rubra as a potential functional food ingredient.